public void InsertRange(int index, IEnumerable <T> collection)
{
InsertRangeCommand command = new InsertRangeCommand(theList, index, collection);
undoManager.Execute(command);
}
public void AddRange(IEnumerable <T> collection)
{
InsertRangeCommand command = new InsertRangeCommand(theList, theList.Count, collection);
undoManager.Execute(command);
}